RF 200-800mm: 500mm vs 800mm etc with Birds

[AlanF]

I have been testing the RF 200-800mm with bird shots to see whether the 500-800mm range justifies the extra weight and bulk over the RF 100-500mm with the R5. @docsmith has provided some good exchanges in other threads and we seem to be in agreement with how focal length affects IQ and resolution. My original comparisons were directly with the RF 100-500mm.The RF 200-800mm at 500mm is as good as the RF 100-500mm and so to make things consistent I'll post some comparative images from just the RF 200-800mm at different focal lengths of compliant birds that stayed in the same place for long enough. You can draw your own conclusions, but here are mine in a nutshell.

For perched birds, the increase in resolution from 500-800mm is not that much, although more pixels are put on the image. It is easier at long distances for eyeAF to work for the longer lens, though at those distances a centre single point square is usually adequate. The consistency of focus is superb.

For Birds in Flight, 800mm was good for very slow flying birds at long distances, and the birdAF picked them out better against backgrounds. However, for close up ones, I find it difficult to keep them in frame and in the AF didn't seem to work fast enough to keep them in focus. Zooming out to 500 or 600mm did give me very good results.

As far as weight is concerned, I have no problems hiking with the lens on a sling, but holding it up at an angle was wearing for me.

 

[AlanF]

Goldfinch on feeder. First the full scenes at 500mm and 800mm, and then crops at 500, 600, 672, 707 and 800mm.

 

[AlanF]

Robin on tree. First the full scenes at 500mm and 800mm, and then crops at 400, 500, 600, 672, 707 and 800mm.

 

[AlanF]

Grey Heron. First the full scenes at 500mm and 800mm, and then crops at 400, 500, 600, 707 and 2 at 800mm.

 

[AlanF]

An increase in focal length will resolve more detail when there is fine detail that is just under the resolution power at the shorter focal length. From my charts, I estimate that the 200-800mm at 800mm could give up to about 25% extra resolving power, and not the 60% you would expect from the 60% increase in focal length over 500mm, and the 1.4xTC on the 500mm significantly less. In the images I have just posted, there is not much detail lurking under the 500mm focal length that can be brought out by the extra 25%. In some cases, there will be and you will see the difference. The shots at 400mm are detectably less well-resolved. Extenders and increasing focal length do have windows where they do show their advantages, but those windows are often not there in much of what we shoot.

 

[docsmith]

Thanks for the pictures and analysis Alan! But, just playing with the thought that 500 to 800 gives you 25% gain in resolution, not 60%. Even if correct, 25% extra resolution is like taking the 45 MPs on the R5 and going to a 70 MP sensor (assuming equivalent pixels). So, for all these people clamoring for more MP...here's a way to do it.

Yes, I think we are in agreement.

Wanting to take a step back. I created my backyard set up over a decade ago. I would take some photos with 100-400 I, Sigma 150-600S, and even 100-400 II. All good to great lenses in their own right and I've used each in a variety of ways.

But, it wasn't until I had the 500 f/4 II plus 1.4tc that I started to get consistently good images at my backyard set up.

The 100-500 aside (as will be testing it later), the RF 200-800 at 500-800 mm is doing what it took my 500 f/4 II to do, allowing me to sit a reasonable distance from my feeder (~30 ft), and get images I like of birds on the perch I made.

So, great lens. A definite tool that I will recommend to others.

So, a few more pics for people to consider at different focal lengths at my backyard set up.

@ 600 mm
cropped/processed in LR to a headshot to show detail.

Cropped showing full cardinal:



Unprocessed (I actually have a Junco headshot series from 600 to 800....but I think people have seen enough unprocessed Junco headshots that show the same level of detail)


@ 800 mm



The RF 200-800 is sharp enough at 600 mm that along with the R5 it is doing what several other lenses before it didn't. With 700 and 800 mm I am reaching out to the trees behind my feeder better than ever.

So, great lens. I am enjoying it. The AF needs light, but once it has light, it is good.

 

[scyrene]

Thanks for doing this, everyone. Although it doesn't really affect my desire for the lens, I always like to see images taken with kit before I get it, especially from competent users!

 

[AlanF]

You can pick up a small bird like this at 800mm, identify it as a Green Sandpiper, and then enlarge 4x!

 

[AlanF]

Or you can pick up a Red Kite miles away and even upscale by 2.

 

[docsmith]

@AlanF something that you mentioned made me think of a calculator I created a while ago. Basically, I tried to estimate pixels per inch at different focal lengths for a subject certain distances from where I am.

Regarding the R5 and it's 8192x5464 pixel resolution:

Focal Length (mm)	Width of frame (ft) captured at 30 ft to subject	Pixels per Inch
300​	3.6​	189.6​
400​	2.7​	252.8​
500​	2.2​	316.0​
560​	1.9​	354.0​
600​	1.8​	379.3​
700​	1.5​	442.5​
800​	1.4​	505.7​
1000​	1.1​	632.1​
1120​	1.0​	708.0​

So, how many pixel per subject inch do you need to properly render a bird? Oddly, this gets back to the debate, but you can see the classic 150 ppi and 300 ppi coming into play here. So, for my set up, assuming the answer is 300 ppi, I need a 500 mm lens that outperforms my R5 sensor. So, it seems the RF 200-800 does just that. It also explains why it was as soon as I had a 500 f/4 II I started getting images I liked. It also tells me that the Sigma 150-600S, EF 100-400 II plus 1.4TC likely underperform the sensor.

But, if I am happy with 300 ppi, of course I am not seeing much difference between 600 mm and 800 mm. It just tells me that the RF 200-800 does a reasonable job of rendering with the R5 sensor.

So, next question, at what distance does each focal length cross the 300 ppi threshold:

Focal Length (mm)	Distance 300 ppi on R5 sensor (ft)
500	31.6
560	35.4
600	37.9
700	44.2
800	50.6
1000	63.2
1120	70.8

These are ideal calcs. I am not saying that the RF 200-800 out resolves the R5 sensor at all focal lengths. But, looking at Bryan's data at TDP, it is pretty good at 600 mm, under resolving for sure at 800 mm. Based on my images and others I have seen here, 700-750 mm is pretty good too (Bryan didn't test between 600 and 800 mm). So, a guess, but the RF 200-800 has a reasonable chance of going out to ~45 ft with ~300 ppi resolution. Using focal lengths beyond that (plus 1.4TC), I am likely getting less than 300 ppi resolution. Thus, no good for smaller birds, but ok for larger subjects.

Oof...that is a lot of math without any pictures. A Eastern Bluebird. EXIF data tells me 15.1 m (give or take, EXIF data seems to work in blocks, not specific), but if close to accurate, that is 49 ft. There is still good detail there (taken @ 800 mm)

 

[AlanF]

@AlanF something that you mentioned made me think of a calculator I created a while ago. Basically, I tried to estimate pixels per inch at different focal lengths for a subject certain distances from where I am.

Regarding the R5 and it's 8192x5464 pixel resolution:

Focal Length (mm)	Width of frame (ft) captured at 30 ft to subject	Pixels per Inch
300​	3.6​	189.6​
400​	2.7​	252.8​
500​	2.2​	316.0​
560​	1.9​	354.0​
600​	1.8​	379.3​
700​	1.5​	442.5​
800​	1.4​	505.7​
1000​	1.1​	632.1​
1120​	1.0​	708.0​

So, how many pixel per subject inch do you need to properly render a bird? Oddly, this gets back to the debate, but you can see the classic 150 ppi and 300 ppi coming into play here. So, for my set up, assuming the answer is 300 ppi, I need a 500 mm lens that outperforms my R5 sensor. So, it seems the RF 200-800 does just that. It also explains why it was as soon as I had a 500 f/4 II I started getting images I liked. It also tells me that the Sigma 150-600S, EF 100-400 II plus 1.4TC likely underperform the sensor.

But, if I am happy with 300 ppi, of course I am not seeing much difference between 600 mm and 800 mm. It just tells me that the RF 200-800 does a reasonable job of rendering with the R5 sensor.

So, next question, at what distance does each focal length cross the 300 ppi threshold:

Focal Length (mm)	Distance 300 ppi on R5 sensor (ft)
500	31.6
560	35.4
600	37.9
700	44.2
800	50.6
1000	63.2
1120	70.8

These are ideal calcs. I am not saying that the RF 200-800 out resolves the R5 sensor at all focal lengths. But, looking at Bryan's data at TDP, it is pretty good at 600 mm, under resolving for sure at 800 mm. Based on my images and others I have seen here, 700-750 mm is pretty good too (Bryan didn't test between 600 and 800 mm). So, a guess, but the RF 200-800 has a reasonable chance of going out to ~45 ft with ~300 ppi resolution. Using focal lengths beyond that (plus 1.4TC), I am likely getting less than 300 ppi resolution. Thus, no good for smaller birds, but ok for larger subjects.

Oof...that is a lot of math without any pictures. A Eastern Bluebird. EXIF data tells me 15.1 m (give or take, EXIF data seems to work in blocks, not specific), but if close to accurate, that is 49 ft. There is still good detail there (taken @ 800 mm)

View attachment 214633

Inches? The rest of the world gave those up decades or centuries ago. My rule of thumb is that 1000px along the length of a bird gives me an adequate image for a postcard., 1500px is getting pretty sharp and 2000 is good for most detail and anything more than that a bonus.

 

[docsmith]

I am old school